STATEN ISLAND, N.Y. -- With a confession by the alleged killer of Etan Patz this week, the 33-year-old mystery of the tragic disappearance and apparent death of the little boy turns to prosecution of the crime -- and a possible hunt for Etan's remains.

But locating the body -- perhaps buried deep in the former Fresh Kills landfill -- and convicting former bodega worker Pedro Hernandez in Patz's May 25, 1979, disappearance after his confession to NYPD detectives could prove difficult if not impossible.

In announcing the arrest of Hernandez, NYPD Commissioner Raymond Kelly told reporters it was "unlikely" the remains of the 6-year-old boy, lured on his way school to the basement of the SoHo bodega where Hernandez worked, would ever be found.

Hernandez, who was 19 at the time of the alleged crime, told cops he strangled Etan, put his body in a bag and dumped it in the trash a block or so away.

If true, that trash likely would have been hauled to Fresh Kills, either by the city Department of Sanitation or a private carter.

But DOS spokeswoman Kathy Dawkins declined to respond directly to questions about whether the NYPD has approached Sanitation regarding a search for Etan's remains -- or even whether Sanitation has a record of where trash was dumped by date, including the late-May to early-June 1979 period.

"At this point, all I can say is we are fully cooperating with the police in their investigation," repeated Ms. Dawkins.

The NYPD did not respond to queries about whether a look at Fresh Kills is under way or being considered.

That lack of physical evidence, more than three decades later, could make prosecution of Hernandez, now 51, tough, legal experts here suggest.

"You can successfully prosecute someone for murder based on circumstantial evidence," said one longtime Staten Island prosecutor, "but you have to have more than just a confession. I am sure they have something else in this case. Perhaps the defendant gave a specific detail about the crime which was never made public and that matched with other circumstantial evidence."

Mario Galluci, a Willowbrook defense attorney and former prosecutor, looked at the case from both sides.

"As a prosecutor, it would be very difficult," said Gallucci. "I don't believe you can do it based on a confession alone. You have to have some sort of evidence to substantiate what he said. It would mean police going back and looking at all the interviews they did at the time. Was he late to work? Did he not show up afterward? It would be tough, because you have to try to re-interview anyone from that time who was still around, and still remembered."

Defending Hernandez would include pointing out the lack of physical and forensic evidence, said Gallucci.

"You could also point to serious psychological problems he had in his life, stemming from having been around at the time of this incident, that manifested all these years later into him making a confession and admitting to a crime he didn't commit," suggested Gallucci.

Still, in 2004, Staten Island District Attorney Daniel Donovan's office won the conviction of Andre Rand in the 1981 kidnapping of 7-year-old Holly Ann Hughes of Port Richmond based on circumstantial evidence and statements he made to people. Holly Ann's body was never found, nor was there any forensic evidence tying Rand to her disappearance.

Rand, a sex offender, was also convicted in the kidnapping of another Staten Island child, 12-year-old Jennifer Schweiger, whose remains were later found in a shallow grave on the grounds of the former Willowbrook State School in 1987.

Meanwhile, Advance legal columnist Daniel Leddy, an attorney and former Family Court judge, pondered the case.

"Unless law enforcement has other evidence that it is not disclosing, this will be a very difficult and perhaps even impossible case to prosecute successfully," said Leddy. "Even if the confession withstands what will certainly be an attack on its admissibility, it alone is insufficient as a matter of law to support a conviction."

Pointing to New York Criminal Procedure law, Leddy noted that "no person can be convicted of any offense solely upon evidence or admission made by him without additional proof that the offense charged has been committed," a point that was recently underscored by a New York State Court of Appeals ruling.

However, Leddy said, "It's important to note that a confession need not be corroborated for charges to be brought."

Recalling his time on the Family Court bench, Leddy remembered being "dismayed by the number of parents who waited inordinately long periods of time -- sometimes as much as a year -- to seek warrants for their missing children."

"Almost all these cases involved teenagers, of course," added Leddy, "but they were at significant risk nonetheless. In several cases, it was the parents themselves who created the problem by kicking the youngster out of the house, either temporarily as a punishment or permanently because they no longer wanted him or her."

Such was not the case, of course, with Etan's parents, who remain living on the same block with the same telephone number, which their little boy had memorized, in hopes that one day he would return to them.